The noise made when clicking your fingers is the sound of the finger hitting your palm not the finger and thumb rubbing together.

Yes, I love this one! I never used to be able to click my fingers until I figured this out. Nowadays of course, my finger-snaps are much sought-after by all the top popular music artistes and have featured on many hit records, none of which I can bring to mind presently, for some reason.

That said, I can also produce a reasonably loud noise without using the palm, by forcing the thumbnail back (edit: actually I'm forcing it forward, come to think of it, i.e. towards the palm) and releasing it (whilst ensuring that the finger used doesn't impact the rest of the hand). It's a different quality of sound, but it's similar. I don't have very long thumbnails though; it would be interesting to hear the sound made using this technique on e.g. a two-inch long nail. Or maybe it would just break off? I think I'll try to grow the one on my right thumb in the interests of research.

Isn't the whole point in these things is that they aren't groundbreaking, and people are shocked by their having felt like they were groundbreaking discoveries only for a moment's thought to lead them to believe that no, they're actually "REALLY obvious"?

The only difference with the finger snapping is that most of the posts in these threads have been people making these groundbreaking discoveries and then coming to realise that they aren't groundbreaking away from the forum, then later on posting about it here. With the finger snapping Mark's first post fits this and then you're seeing subsequent people doing the groundbreaking-no-actually-really-obvious thing in almost real time on the forum.

I used to think that your cholesterol level was the level of build-up in your arteries, whereas it's actually just a measure of cholesterol in your blood. What I was thinking of seems to be atherosclerosis.

That's how I found out. That video was going around Facebook and I felt kind of stupid that it hadn't occurred to me that that's what they actually did. Apparently they can fill themselves with air when they are out of water but how often is that gonna happen without human intervention?

This doesn't really fit here, but doesn't exactly deserve a new topic ("possibly not obvious things you've just found out").

I've always detested the smell of melted cheese, especially melted Parmesan cheese. I thought it smelled like vomit and would only eat it under duress. It was pretty much the only food-related thing I didn't really like.

Anyway, I found out yesterday that a principal component of melted cheese - which is especially prominent in Parmesan - is butyric acid, which is also the thing that gives vomit its distinctive smell. So I was right all along. Eating Parmesan cheese is pretty much like eating vomit.

(Also why American chocolate is so foul - contains the same substance).

On a similar culinary note. I've only recently found out when you cook a steak the redness oozing out is not blood it's myoglobin, found in muscle tissue

I legitimately wonder if Michael Calder learned this fact shortly before he filmed the Series 42 grand final (featuring his famous declaration of MYOGLOBIN). I'd say learning it is one of the most common real-life ways to be exposed to the word.

On a similar culinary note. I've only recently found out when you cook a steak the redness oozing out is not blood it's myoglobin, found in muscle tissue

I legitimately wonder if Michael Calder learned this fact shortly before he filmed the Series 42 grand final (featuring his famous declaration of MYOGLOBIN). I'd say learning it is one of the most common real-life ways to be exposed to the word.

I'm not sure how obvious this is, but you know how people say that the three primary colours of light are red, green and blue, and that the three primary colours of pigment are red, yellow and blue? Well, I always thought that was a bit weird, and it turns out that apparently, the three primary colours of pigment are actually magenta, yellow and cyan (which are the secondary colours of light - magenta = blue + red; yellow = red + green; cyan = green + blue). So the red/yellow/blue thing is just a myth.

Astronauts wearing diapers.
Its just the thought of Neil Armstrong and co shitting their pants in them suits sullies my hero worship.
I guess even filmmakers have missed this.
Try watching Gravity ( probably the most over rated film of the last 10 years )